WO2001059960A1 - Compensation optique de l'evanouissement de la puissance du a la dispersion dans des signaux en bande laterale double - Google Patents

Compensation optique de l'evanouissement de la puissance du a la dispersion dans des signaux en bande laterale double Download PDF

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Publication number
WO2001059960A1
WO2001059960A1 PCT/US2001/004327 US0104327W WO0159960A1 WO 2001059960 A1 WO2001059960 A1 WO 2001059960A1 US 0104327 W US0104327 W US 0104327W WO 0159960 A1 WO0159960 A1 WO 0159960A1
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optical
signal
path
optical signal
coupled
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PCT/US2001/004327
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English (en)
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WO2001059960A9 (fr
Inventor
Steven A. Havstad
Asaf B. Sahin
Olaf H. Adamczyk
Yong Xie
Alan E. Willner
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University Of Southern California
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Priority to AU2001238122A priority Critical patent/AU2001238122A1/en
Publication of WO2001059960A1 publication Critical patent/WO2001059960A1/fr
Publication of WO2001059960A9 publication Critical patent/WO2001059960A9/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
    • H04B10/2519—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using Bragg gratings

Definitions

  • This application relates to optical signal transmission and detection over dispersive optical links such as optical fibers .
  • An optical wave at an optical carrier frequency f c may be modulated at a subcarrier frequency f RF to produce two modulation sideband signals at frequencies of (f c -f RF ) and ( f c + y &F ) r respectively.
  • the sideband signals may be used to carry information for transmission over an optical link or a network of optical links.
  • the optical media in an optical link e.g., optical fibers, may exhibit chromatic dispersion where spectral components at different frequencies in an optical signal can travel at different group velocities. Therefore, in optical systems where double-sideband signals are used, the two sideband signals at different frequencies of (f c -f RF ) and
  • ⁇ l- (f c +f RF ) in an optical signal may be delayed relative to each other.
  • FIG. 1 illustrates this dispersion-induced power fading effect in a double- sideband optical signal.
  • This signal fading is undesirable in many applications because it can seriously deteriorate the detection of the optical signals.
  • power fading may dynamically change, with the transmission distance. Therefore, it may be desirable to provide distance- independent power fading compensation in some microwave- and millimeter-wave-based optical systems that use double-sideband signals to transmit information.
  • a tunable optical dispersion element such as a nonlinearly-chirped fiber Bragg grating, may be used to produce the desired dispersion.
  • FIG. 1 illustrates the distance-dependent power fading in a double-sideband optical signal caused by the chromatic dispersion in an optical transmission medium.
  • FIG. 2 illustrates one embodiment of an optical device that provides distance-independent compensation for the distance-dependent power fading in a double- sideband optical signal transmitting through a dispersive optical link.
  • FIG. 3 shows one implementation of the optical device shown in FIG. 2.
  • FIG. 4A shows one embodiment of a tunable optical dispersion element in the device shown in FIG. 3 where a nonlinearly-chirped fiber Bragg grating is used.
  • FIGS. 4B and 4C illustrate operations of the nonlinearly-chirped fiber Bragg grating in compensating for the distance-dependent power fading.
  • FIGS. 5, 6, and 7 show various measured signals obtained from a device based on the design shown in FIG. 3.
  • FIG. 8 shows another implementation of the optical device shown in FIG. 2. Detailed Description
  • FIG. 2 shows one embodiment of an optical device 200 that provides distance-independent compensation for the distance-dependent power fading in a double-sideband optical signal transmitting through a dispersive optical link.
  • the optical signal at the optical carrier frequency f c has two modulation sidebands at (f c -f RF ) and (f c +f RF ) that include the information or data to be transmitted.
  • the subcarrier frequency f RF may be generally in the frequency range for the microwave and millimeter-wave frequencies, e.g., from tens of kilohertz ( ⁇ 10 4 Hz) to hundreds of gigahertz (-10 11 Hz) .
  • the device 200 uses a phase diversity configuration with two separate optical paths 210 and 222 to perform the compensation for the distance-dependent power fading.
  • the device 200 includes an optical input port 201 for receiving the double-sideband optical signal from the dispersive optical link and an optical output port 202 for combining the optical signals from the two paths 210 and 220 to produce the fading-compensated optical output.
  • the input port 210 is designed to split the input signal into the two separate optical paths 210 and 220.
  • a tunable optical dispersion element 212 is placed in one optical path, e.g., the optical path 210, to introduce different time delays for the two different frequencies of (f c -f RF ) and (f c +f RF ) so that the sum of the phases of the modulation sidebands in the optical path 210 relative to the phase of the optical carrier at the carrier
  • the optical dispersion element 212 may be tunable in order to produce this desired relative
  • This optical device 200 further includes a polarization control mechanism to control the polarization of light in at least one optical path so that the optical signals in the two optical paths 210 and 220 have orthogonal polarizations relative to each other at the output port 202 where the two optical paths 210 and 220 are coupled together.
  • a polarization rotator or controller may be placed in one of the two optical paths to achieve this condition.
  • optical signals in the two paths 210 and 220 can be combined at the output port 202 without substantial cross-talk effects that would otherwise be present due to optical coherence.
  • an optical receiver that receives the combined optical signal from the output port 202 produces a detector output that is a sum of the individual powers of the two optical signals from the two optical paths .
  • the photocurrents representing the two optical signals can be written as:
  • the condition of ( ⁇ g - ⁇ 0 )
  • ⁇ /2 may be achieved by controlling the relative optical path length difference of the two optical paths 210 and 220.
  • the operation of the device 200 is independent of the state of accumulated dispersion in the received double-sideband optical signal. Therefore, the device 200 may be deployed at any desired location in an optical link within an optical network to compensate for the distance-dependent power fading.
  • FIG. 3 shows one exemplary optical device based on the design shown in FIG. 2 for installation in a fiber link 350 that carries a double-sideband optical signal
  • This device includes an input fiber optical coupler 300 as its input port to receive the optical signal 352.
  • the input coupler 300 is coupled to receiving terminals of two separate fiber optical paths 310 and 320 and is operable to split the input optical signal 352 into two optical signals 301 and 302 in the fiber optical paths 310 and 320, respectively.
  • the optical path 310 includes a tunable optical dispersion element 314 and a control unit 316 that controls the operation of the element 314.
  • the element 314 is operable to produce different dispersions on spectral components at different wavelengths in the optical signal 301 to produce a dispersion-modified signal 301A in which the sum of the phases of the modulation sidebands relative to the phase of the optical carrier at the carrier frequency f c is shifted by ⁇ with respect to the sum of the phases of the modulation sidebands in the optical signal 302 relative to the optical carrier at the carrier frequency f c in the optical path 320.
  • An output optical fiber coupler 330 is used to couple the output terminals of the fiber optical paths 310 and 320 to combine the signals 301A and 302 into an output optical signal 303.
  • An optical polarization- rotating element 318 is implemented in either one of the optical paths 310 and 320 to make the polarizations of the signals 301A and 320 orthogonal to each other at the output coupler 330.
  • a fiber polarization controller or a 90-degree polarization rotator may be used as the element 314 and placed in the optical path 310 between the optical dispersion element 314 and the output coupler 330.
  • the polarization of the signal 301A is rotated by 90 degrees to produce a polarization- rotated signal 301B.
  • the signals 301B and 320 is then combined at the coupler 330 to produce the output signal 303.
  • An optical receiver 340 may be coupled to receive the signal 303.
  • optical paths 310 and 320 are designed to have different optical path lengths so that the phase associated with the path length difference at the output
  • variable optical delay element 322 such as a fiber loop with a fiber stretcher, may be placed in one optical path, e.g., 320, to adjust the phase difference
  • an optical attenuator 324 may be placed in at least one of the optical paths 310 and 310 to satisfy this condition.
  • the tunable dispersion element 314 is a nonlinearly-chirped fiber Bragg grating (FBG). See, U.S. Patent No. 5,982,963 to Feng et al .
  • the nonlinearly-chirped Bragg grating 410 is a grating that can be formed along an optical waveguide, e.g., an optical fiber, and has a grating parameter ri neff (z) ⁇ ( z) that changes nonlinearly with the position z along the fiber optic axis, where n neff (z) is the effective index of refraction and ⁇ (z) is the period of the grating.
  • the grating 410 has a long-wavelength end 411 and a short-wavelength end 412 where the grating
  • this nonlinearly- chirped grating 410 may be used to receive an optical signal and to reflect light satisfying a Bragg condition
  • the relative group delays for different spectral components at different wavelengths are different and tunable in the nonlinearly- chirped fiber grating, that is, the grating dispersion is tunable by adjusting the grating parameter n neff ( z) ⁇ (z) .
  • This is caused by the nonlinearity in the chirp of the grating parameter n neff (z) ⁇ (z) .
  • a grating control unit 420 which is part of the control unit 316 in FIG. 3, may be coupled to the grating 410 to change the grating parameter n neff ( z ) ⁇ ( z ) so as to shift the center
  • This grating control unit 420 may be a fiber stretcher to control the total length of the fiber
  • an optical circulator 312 may be used to couple the tunable fiber grating 314 to the optical path 310 so that the signal 301 is directed to a receiving end of the grating 314 (either 411 or 412) and the reflected signal 301A is coupled into the optical path 310 towards the output coupler 330.
  • FIG. 4C illustrates the operation of the fiber grating 410 for compensating the power fading in the device in FIG. 3.
  • the short-wavelength end 412 is used to receive the signal 301 and to produce the signal 301A in the optical path 310.
  • the modulation sideband signals are at different frequencies (f c +f RF ) and (f c -f RF ), they are reflected at different positions in the fiber grating 410 as illustrated in FIG. 4A to produce different delays ⁇ i and ⁇ 2 relative to the optical carrier at the optical carrier frequency f c .
  • Such grating-induced delays are added to the relative delays ⁇ 'i and ⁇ ' 2 caused by the chromatic dispersion in the fiber link so that the total relative delays of the modulation sideband signals with respect to the optical carrier in the optical signal 301B at the output coupler 330 are ( ⁇ i+ ⁇ 'i) and ( ⁇ ' 2 + ⁇ 2 ), respectively.
  • the modulation sideband signals at sideband frequencies (f c +f RF ) and (f c -f RF ) in the signal 302 in the optical path 320 also have the relative delays ⁇ 'i and ⁇ ' 2 respect to the optical carrier caused by the chromatic dispersion in the fiber link.
  • the total relative delays of the modulation sideband signals with respect to the optical carrier in the optical signal 302 at the output coupler 330 are ( ⁇ ti+ ⁇ 'i).
  • the overall length of the fiber grating 410 is controlled so that the phase delay corresponding to the total relative delay in time, ( ⁇ + ⁇ 2 ) , is ⁇ . If there is any additional relative delay between the sidebands and the carrier in the optical signals 301B and 302 at the output coupler 330 due to dispersion in the paths 310 and 320 that is not caused by the fiber grating 410, the grating-induced phase delay corresponding to the total relative delay ( ⁇ + ⁇ 2 ) may be different from ⁇ .
  • the fiber grating 410 is tuned to produce a total relative delay ( ⁇ + ⁇ 2 ) so that, at the output coupler 330, the sum of the phases of the modulation sidebands relative to the phase of the optical carrier at the carrier frequency f c is shifted by ⁇ with respect to the sum of the phases of the modulation sidebands in the optical signal 302 relative to the optical carrier at the carrier frequency f c in the optical path 320.
  • FIG. 5 compares magnitudes of the power fading in a double-sideband optical signal after transmission over a dispersive fiber of 150 km in length with and without the above power fading compensation.
  • the subcarrier frequency is 8 GHz.
  • the above compensation scheme essentially eliminates the power fading and achieves a power uniformity within ldB over the 150-km fiber.
  • FIG. 6 shows the results when the subcarrier frequency is 12 GHz .
  • FIG. 7 further shows measured bit error rates after transmission over dispersive fibers of 27.7 km and 52.4 km in length for a double-sideband signal modulated at a subcarrier frequency of 8 GHz.
  • the carrier is modulated to carry 155-Mb/s pseudorandom data.
  • 0 Jem corresponds to maximum power fading in the grating path of our module
  • 52.4 km corresponds to maximum power fading in the nongrating path.
  • BER performance is independent of whether the received electrical subcarrier power originated from the grating path or the nongrating path.
  • the 3-dB optical power penalty 6-dB electrical power penalty
  • relative to a back-to-back BER measurement comes from optical power splitting in the device shown in FIG. 3.
  • FIG. 8 shows an implementation of the device shown in FIG. 3 where the two terminals 411 and 412 of the tunable fiber grating 410 are coupled to both optical paths 410 and 420, respectively.
  • a second optical circulator 810 is used to couple the terminal 412 of the fiber grating 410 to the second optical path 320. Since the dispersions produced by the two terminals 411 and 422 are opposite, the fiber grating 410 can be stretched to

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention porte sur des techniques et des dispositifs de compensation optique de l'évanouissement de la puissance, dû à la dispersion, dans des signaux en bande latérale double, se basant sur un élément accordable de dispersion optique (Figure 3).
PCT/US2001/004327 2000-02-08 2001-02-08 Compensation optique de l'evanouissement de la puissance du a la dispersion dans des signaux en bande laterale double WO2001059960A1 (fr)

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AU2001238122A AU2001238122A1 (en) 2000-02-08 2001-02-08 Optical compensation for dispersion-induced power fading in optical transmission of double-sideband signals

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US18111900P 2000-02-08 2000-02-08
US60/181,119 2000-02-08

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CN114050873A (zh) * 2021-11-10 2022-02-15 中国人民解放军空军工程大学 基于色散补偿技术的远程微波频率测量装置及方法

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US6850712B1 (en) * 2000-05-31 2005-02-01 Lucent Technologies Inc. Optical fiber transmission system with polarization multiplexing to reduce stimulated brillouin scattering
JP4004720B2 (ja) * 2000-08-09 2007-11-07 富士通株式会社 波長分散測定装置及びその方法
GB0021976D0 (en) * 2000-09-07 2000-10-25 Optomed As Multi-parameter fiber optic probes
US6633704B2 (en) * 2001-04-30 2003-10-14 Corning Incorporated Chromatic dispersion compensator
WO2002088805A1 (fr) * 2001-04-30 2002-11-07 Corning Incorporated Compensateur de dispersion chromatique
US6775631B2 (en) * 2001-12-17 2004-08-10 Nortel Networks Limited Post detection chromatic dispersion compensation
US6829549B2 (en) * 2001-12-17 2004-12-07 Nortel Networks Limited Implementation of a post detection chromatic dispersion compensation transfer function
US20040057734A1 (en) * 2002-09-25 2004-03-25 Lucent Technologies, Inc. Method and system for reducing transmission penalties associated with ghost pulses
US7391977B2 (en) * 2003-03-12 2008-06-24 General Photonics Corporation Monitoring mechanisms for optical systems
US7952711B1 (en) 2007-03-26 2011-05-31 General Photonics Corporation Waveplate analyzer based on multiple tunable optical polarization rotators
US8422882B1 (en) 2008-02-04 2013-04-16 General Photonics Corporation Monitoring polarization-mode dispersion and signal-to-noise ratio in optical signals based on polarization analysis
US20100239245A1 (en) * 2009-03-21 2010-09-23 General Photonics Corporation Polarization Mode Emulators and Polarization Mode Dispersion Compensators Based on Optical Polarization Rotators with Discrete Polarization States
US8780433B2 (en) 2011-09-28 2014-07-15 General Photonics Corporation Polarization scrambling based on cascaded optical polarization devices having modulated optical retardation
JP2013078093A (ja) * 2011-09-30 2013-04-25 Fujitsu Ltd 光受信装置および光ネットワークシステム
US9671673B2 (en) * 2014-11-17 2017-06-06 Singapore University Of Technology And Design Optical device for dispersion compensation
US10404397B2 (en) * 2015-12-23 2019-09-03 Adva Optical Networking Se Wavelength division multiplexed telecommunication system with automatic compensation of chromatic dispersion
US10122460B2 (en) 2017-01-13 2018-11-06 Adva Optical Networking Se Method and apparatus for automatic compensation of chromatic dispersion
JP6946360B2 (ja) * 2019-02-01 2021-10-06 株式会社Ｋｄｄｉ総合研究所 光受信器及び光伝送方法
CN113691314B (zh) * 2020-05-18 2022-11-22 西安电子科技大学 一种微波、毫米波信号的光子线性变频及光纤传输方法
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Publication number Priority date Publication date Assignee Title
CN114050873A (zh) * 2021-11-10 2022-02-15 中国人民解放军空军工程大学 基于色散补偿技术的远程微波频率测量装置及方法
CN114050873B (zh) * 2021-11-10 2023-09-12 中国人民解放军空军工程大学 基于色散补偿技术的远程微波频率测量装置及方法

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US20010035996A1 (en) 2001-11-01
WO2001059960A9 (fr) 2002-10-24
AU2001238122A1 (en) 2001-08-20

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